Soliton pulses propagating in optical fiber are well known. See, for instance, U.S. Pat. No. 4,406,516. Such solitons have been shown to be robust against a variety of perturbations, and consequently are being considered for high bit rate, long distance transmission in optical fiber communication systems. See, for instance, L. F. Mollenauer et al., Optical Fiber Telecommunications IIIA, J. P. Kaminow and T. L. Koch, editors, Academic Press, San Diego, 1997, especially pp 373-460.
As is well known, optical solitons propagating in a homogeneous medium (such as conventional optical transmission fiber) represent a balance between the medium's non-linearity and its dispersion. Standard optical solitons are solutions of the nonlinear Schrodinger equation.
It has been recognized that soliton pulses may be manipulated by providing a transmission medium with non-constant dispersion. See, for instance, S. V. Chernikov et al., J. of the Optical Society of America, B, Vol. 8(8), pp. 1633-1641, August 1991, and P. V. Mamyshev et al., IEEE J. of Quantum Electronics, Vol. 27(10). pp. 2347-2355, October 1991. The former reference discloses adiabatic soliton pulse compression in fiber with slowly decreasing dispersion. Experimental results on soliton pulse compression in optical fiber with decreasing dispersion are disclosed, for instance, by S. V. Chernikov et al., Electronics Letters, Vol. 28(19), p. 1842, September 1992; S. V. Chemikov et al., Optics Letters, Vol. 18(7), p. 476, April 1993; S. V. Chernikov et al., Electronics Letters, Vol. 30(5), p. 433, March 1994; and S. V. Chemikov et al., Electronics Letters, Vol. 28(13), p. 1210, June 1992.
Soliton compression is of interest for very high bit rate optical fiber communication systems because it can yield pulses of substantially lower pulse width than can be obtained by laser modulation. However, because of the inherently small dispersion in standard optical fiber, the typical lengths of the dispersion-decreasing fiber for picosecond soliton pulses are undesirably long, exemplarily a few kilometers. Thus, it would be advantageous to have available a technique for compression of optical pulses that yields soliton pulses and that does not include the use of long lengths of dispersion-decreasing fiber. This application discloses such a technique.
It is known that periodic media such as fiber Bragg gratings (FBGs) or photonic crystals can exhibit strong dispersion, especially in the spectral region close to the reflection band of the medium. Non-linear pulse evolution in periodic media has been studied by B. J. Eggleton et al., Physical Review Letters, Vol. 76(10), p. 1627, March 1996, and by B. J. Eggleton et al., J. Optical Soc. of America B, Vol. 14(11), p. 2980, November 1997. Fiber grating non-soliton pulse compressors are disclosed in G. Lenz et al., J. Optical Soc. of America, Vol. 15(2), p. 715, February 1998. See also U.S. patent application Ser. No. 08/989,093 filed Dec. 11, 1997 by B. J. Eggleton et al., and N. M. Litchinitser et al., J. Lightwave Technology, Vol. 15(8), page 1303, August 1997. FIG. 1 of the latter schematically shows a transmissive dispersion compensator for re-compression of non-soliton pulses.